- Then I cut parts of the potato using a cork borer and knife to equal masses keeping the surface area even
- Taking a test tube rack I placed 6 test tubes and then labelled them 0.2m, 0.4m, 0.6m, 0.8m and 1m.
- Then I got 0.2m, 0.4m, 0.6m, 0.8m and 1m salt solution concentrations.
- I then weighed every potato chip to see if all potato chips weighed the same on an electronic balance and recorded the weights.
- I then put the 6 potato chips which are roughly the same mass into the 6 test tubes.
- Whilst waiting I set out some paper towels with which I was going to dry the paper and I drew up a basic table for my results.
- After 2 to 3 hours I drained out the solutions in the sink and placed all the chips on the paper towel in the order I had put them in the test tubes as to not confuse myself as to which chip came from which solution.
- I dried each chip with the paper towel and then placed each one on the scales so that I could weigh them.
- Each potato was measured accurately on the electronic scales and then the weights were recorded.
- Then I redid the experiment under exactly the same conditions. This gave me secondary set of results which gave me a more accurate view on the changes.
Plan/Measurements:
I will record the experiment two times to get accuracy in the mass. I will have six test tubes with the same amount of liquid but the salt concentration will vary from 0m to 1m. I will try to have the potato chips around the same size, so it would be a fair test. I will also keep the potato chips in the test tubes for the same amount of time to make it a fair test.
Fair Test:
To keep it a fair test I will carry out the experiment for the same amount of time, use the same solution and also use the same amount of solution. Also I will keep the potato chips the same size, so if one potato chip is heavier than the other, osmosis will happen much quickly therefore not making it a fair test.
Also I will use the same potato, this is because if I used two different potatoes for the experiment many things might change the experiment like the potatoes age or size also one potato might have more water than the other potato. I will also keep all six test tubes in the same place at the same time during the whole duration of the experiment. To make the experiment as accurate as possible an average will be taken out to both set of results taken.
Accuracy:
For accuracy I will repeat the experiment twice for precise results. I will also blot the chips on to filter paper to get rid of any excess water. The measurements for the solutions had to be perfect as to not change the out come of the experiment. As was stated in my planning section of the coursework, I had to keep all of the different non-variables the same, to make sure that none of them affected the results of the experiment in any way.
Safety:
For safety, I made sure that I carried out the experiment safely, by making sure that the area where the experiment is taking place is cleared from coats and bags and any other unnecessary equipment. I also made sure that I had the correct equipment. I also took extra care of the test tubes because they are made of glass which makes them very fragile to any force put on to the test tubes. Also I will be very careful not to get any of the salt solution concentrations in to my mouth or any other student’s mouth, if the salt solution concentrations would get in to my or any other student’s mouth it could harm the body of mine or any other student’s. I will also be washing all the equipment with water to protect any germs getting to any student. The potato is must clean equipment because the potato could be very dirty and very unhygienic, so the potato must be thoroughly washed before touching it. I had to ensure that every time I handled the potatoes my hands were clean and dry. This was to stop any kind of contamination and made sure that I did not pass on any extra water onto the potato. Whilst cutting the potato, extreme care and precision had to be taken with the cork borer and knife as it is very sharp and could easily cause a serious wound.
Apparatus:
-Test tube rack
- Six test tubes
- Cork Borer
- Weighing Scale
- Tile
- Potatoes
- Six potato chips
- Measuring Cylinder
- Salt Concentration
- Stopwatch
- Distilled water
- Knife
Main Practical:
Results Table:
Practical 1:
Practical 2:
Graph Analysis/Conclusion:
The evidence obtained from this investigation supports the prediction I made. It also shows that the potato chips increased mass in solutions because the lower the concentration of the salt solution in the test tube the larger the mass of the potato will be. This is because the water molecules pass from a high concentration, therefore, the chips in higher water concentrations will have a larger mass than in higher salt concentrations. The graph shown gives the line of best fit for the percentage change in mass of the potato chips over the course of the two to three hour experiment. The graph is a curve that slopes downwards and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain and loss in mass and concentration are not directly proportional. However, there is a pattern on my graph, and this is, as the concentration of the solution increases, the percentage change in mass decreases. The graph shows that the percentage gain and loss in inversely proportional to the concentration. The gradient does change in my graph, from my graph I also saw that the purer the water the higher the mass of the potato chips. In this experiment, I believe that I have collected enough data to support my prediction. This investigation was I think successful, because my results were the same as my predictions. From my graph I can see that as the amount of water increased the amount of osmosis taking place. Also from my graph it shows that the potato tissues increase in mass in solutions with a high water concentration and decrease in mass in solutions with a low water concentration. From right to left the first two points on the graph are very spread out indicating that there was a large change in the mass. At 0m the potato chip gained an average of 0.5g. At 0.2m the potato chip also gained an average of 0.1g. From 0.4m to 1m the potato chips lost mass from 0.3g to 0.65g. The graph and my results tables show that osmosis actually took place in the experiment. As the salt solutions increased, the mass of the potato chip decreased. The trend shown here was that as the concentration of the solution decreases the increase of the weight of the potato increased. I believe that the trend show here happened because there was about the same amount of water in the potato as there was in the solution. The graph shows a clear indication that there was an overall decrease in mass during the experiment. None of my results seem to be different from my predictions and I also I didn’t find any anomalous results where I had to repeat any of my experiments more than twice.
Evaluation:
I believe I gained accurate and sufficient enough results, shown on my graph and tables that concludes the experiment, and to prove my prediction, which allowed me to create an informative graph. My final results were very reliable, due to safety measures I took to make this a fair test. Looking at the overall experiment I have thought of a number of improvements to give me more and better accurate results. Firstly the concentrations were measured using a measuring cylinder, which I think was the right equipment used. Also I think I took easily enough results for the amount of concentrations that I was using, and the time that I used for the experiment to last was enough to allow sufficient osmosis to occur. However if I was to repeat the experiment I might well increase the time of the result to allow more osmosis to happen and possibly find out the saturation point of the chips. Furthermore when the potato was dried to remove surface liquid it was not necessarily done the same on each potato, a more accurate and better way of drying the potato would improve the accuracy further. Also to make this experiment better, I could have done one test at a time, so instead of me hurrying to dry the potato and get it out of the test tube and into the weighing scale I could do one test at a time which would make it easier for me because I don’t have to hurry and dry the potato and weigh it instead I could take my time and not let the other results vary because I would be doing one test at a time. I also could of changed the variables for the experiment, for example instead of changing the mass of the potato I could of used a different variable like using two different potatoes, for example a new potato and an old potato. Also, the cutting of the potatoes was the most difficult part of the experiment as although I was recording my results by mass, it could well have affected the surface area and so the overall rate of osmosis. If I were to repeat the experiment I would have possibly found a machine to cut the potato as it would ensure that all potatoes would be the same weight, as well as the potato I could have found a more accurate way to measure out the solutions and to determine the salt concentrations. Perhaps I could have used a burette. This would ensure that I have an accurate amount of fluid in each test tube. I could also weigh each chip on a more accurate scale, e.g. not to 0.00g but to 0.0000g. The procedure I followed turned out to be correct. My data had no errors and the experiments turned out to be a success. This was because I kept all the potato chips in their concentrations for about the same time length. Also I kept the mass of each potato chip roughly the same, and I kept them all in 20cm3 of solutions. For next time I could make it more accurate by measuring the length of the potato chips as well as the mass. I also could have extended the experiment by using more salt solution concentrations, for example I could have used 1.2, 1.4, 1.6, 1.8 and 2.0m salt solutions which would have produced more accurate results and would have varied my results more. There were not any out of the ordinary results, but some were not as close to the line as others. This may have been caused by human error. When the potato chips were removed from the test tubes and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated I would have found another way to dry the potatoes that would ensure that all were dried in the same way for the same time. I didn’t find any anomalous results, so I didn’t have to repeat the experiment more than twice. However with all this said I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction.
